Prius starting problem! Help!

Try to figure out what you left on in the car. This problem is normally caused by leaving on a light or the headlamps.

Tom

 

Sounds like a classic 12V battery problem. Make sure the terminals are clean and the connections sound. Do you drive far enough to make sure the 12V battery gets charged? If not, leave your Prius running for a few hours to make sure the battery is charged. It doesn't charge very fast from the built-in charger.

Tom

 

i have a 12v problem. it doesn't look like a 12v problem. the huge triangle shows up when you run the car down.. also.. things don't "pop up" that easy.. it takes time to load.. and then eventually triggers the traction battery which helps the system load up.

i've only seen blinking like that after hooking up hooking up the car charger directly to the car. it takes a few tries before the car realized it was only a voltage irregularity and eventually boots up. *shrug*

 

What does that mean, exactly?

Summarizing common causes: 12V battery defective, or failing because it was previously drained; left a door or the hatch not completely closed overnight; poor connection at the 12V battery terminals; charging system problem (not very common); aftermarket or third-party electronics defective or incorrectly installed.

 

There have been a few cases where the -ve battery cable has corroded where it is bolted to the body in the right rear. Easy to check, easy to fix if that's it.

I DO NOT believe the dealer knows how to properly check a battery. I've only seen a few who do. Get a VOM or voltmeter and check it yourself. Before you start the car one morning, check the voltage on the 12V boost terminal under the hood (it's the same point as the battery). You should see AT LEAST 11.8V there, and a normal reading would be 12.5V. If it's down 2V or so you've got a bad battery (dead cell).

 

You might also have an intermittant brake light switch concern. If the ECU doesn't see a brake signal (stepping on the pedal) it will not activate the HV system. When the condition is occuring, does it turn on the main dash lights, but not give a ready light?

 

Were you holding the break all the way in?

 

Sounds like the dealer is clueless or doesn't give two s***s. I'm not sure how comfortable you are working on cars.

In the rear hatch area, near the passenger side tailight, on the interior side near the hatch floor you will see a trim cover. Remove the tray cover first, they carefully pull the trim cover away. Also take out the tray itself.

You should be able to see the motorcycle-sized 12 vdc battery. The pos post is covered by this huge red plastic cover, the neg post is bare. Pos post is towards the front of the car, neg post to the rear of the car

You will notice a tiny cable - more like a wire - going from the neg post to the unitbody. The ring terminal is secured by a bolt. I have noticed corrosion on the bolt threads, which you can't see unless you back the bolt out. So I'm in the habit of backing out that bolt and snugging it back up every 6 months

To check the battery voltage you'll need a DMM (Digital Multi Meter) set on DC volts. That huge red plastic cover is a royal PITA to get off, I buggered mine up when I tried to pry it off.

The proper voltage for a 100% theoretical charge is 12.8-13.2 vdc. You'll need over 12 vdc to boot up the car. If the battery is chronically undercharged, it won't have enough capacity to run the brake boost pump and coolant transfer pump, both of which can contribute to a momentary 40 amp draw

If you feel comfortable removing the hold down clamp and vent tube, I strongly encourage you to remove the battery from the car and properly charge it. The Toyota pdi recommends an automatic battery charger set to 10 amp charge rate

If the battery is badly undercharged, you may need to leave it charging overnight. Once the automatic battery charger indicates full charge, disconnect the charger clamps and leave the battery sitting at least 4 hours, preferably 24 hours, not hooked up to anything.

Then recheck the voltage. A reading of 12.8 and higher is very good, the battery should be ready to work. A reading of 12.4 and under would indicate a bad battery.

As an example, I use VDC Battery Minder float chargers on all my equipment, and the float chargers are always plugged in. If I do a 24 hour resting voltage check, all my batterys will indicate 13.01-13.18 vdc

If the battery indicates full charge, put it back in using the reverse order of removal. Have the fob handy as most likely the alarm will go off once the neg cable is hooked up. My alarm has gone off every time I've put the battery back in

If the battery now works ok, maybe check the voltage a week later just to verify. As David Beale mentioned, you can check using the underhood jump point instead of taking apart the rear hatch area. However, if after a few days the car is dead, you're going to have to check for parasitic loads

I'm still surprised the dealer couldn't check for parasitic loads. Again, I'm afraid you'll have to do this yourself

 

We're all assuming this really is a battery problem. However, if you watch his video the dash lights are fully bright and there is no sign of a struggle for the lights to stay bright. I don't think it was due to a dead battery. I think there could be another intermittent connection involving the computer or the other HSD systems that gave the indication of a fault. The vibration of the towing and the electrical jolt of jump starting the car may have temporarily cleared the problem. That's just pure speculation on my part.

Steve

 

I don't know what's wrong with the forum, but I can't seem to edit my post. Please read the following important safety notice:

Remember that lead acid batteries are DANGEROUS if improperly handled. In normal use they give off hydrogen gas, which is the reason for the vent tube. Batteries also have very high short circuit amperage, say from a dropped wrench across the posts. If the battery explodes, you could be blinded from the acid

 

He did post that the dome light is dim

 

It sounds like you are on your own. It seems as if mechanics no longer rely on common sense

A poor connection or a weak battery can cause all sort of problems with electronics. Once the voltage sags below threshold or gate values, the system may behave in unexpected ways

Around 12 years ago a Boeing 767 had numerous in-flight problems with the autopilot and the display screens going blank, on a flight from Schiphol, Amsterdam to the US. The problems became severe

They declared an emergency and landed at Logan. The investigation revealed a loose battery shunt tie-bar due to improper maintenance

ASN Aircraft accident description Boeing 767-31AER PH-MCH - Boston-Logan International Airport, MA (BOS)

 

Take it to a different dealer. This one either doesn't know enough or doesn't care.

 

Sure sounds like a 12v system issue.... I would recommend a couple of simple checks.
1) check the 12v battery itself. The terminals and the ground wire. be sure they are all tight and clean.
2) check the 12v connection under the hood. The same one you would use if you were going to jump start the car. Make sure it is tight and clean. (saw one from the body shop with that wire loose, caused all sorts of goofy symptoms)
3) FIND A REPUTABLE DEALER!!! If your Prius is still under 3/36 warranty, camp out in the service manager's office and be as politely firm and direct as possible. You might also want to check your owner's manual for the 800-Toyota number and give that a call. You paid for the car and te warranty. YOU DESERVE RESPECT AND A PROPERLY REPAIRED CAR!!